The present invention relates to machine for dispensing a gasketing composition and more particularly the present invention relates to a machine for semi-automatically dispensing a gasketing composition wherein the height of the dispensing means from the part to which the gasketing composition is applied, the traverse speed of travel of the dispensing nozzle means as well the amount of material applied to the part.
Silicone compositions are well known. One type of silicone composition is a room-temperature vulcanizable silicone rubber composition and more particularly a one component group temperature vulcanizable silicone rubber composition. Generally, such one component room temperature vulcanizable silicone rubber (hereinafter referred to RTV) compositions comprises as the basic ingredients, a silanol end-stopped diorganopolysiloxane polymer having a viscosity varying anywhere from 500 to 500,000 centipoise at 25.degree. C. where the organic groups are any monovalent hydracarbon radical but more preferably methyl and phenyl. In the most prevalent of such systems, the crosslinking agent is methyltriacetoxy silane. Although there are various other types of systems which are well-known and generally comprised as a cross-linking agent and an alkoxy silane an amide functional silane, an aminoxy functional silane, and other types of functionalities for the silane cross-linking agent. Usually, such as silane cross-linking is used in the concentration of 1 to 15 parts per 100 parts of the base silanol end-stopped diorganopolysiloxane polymer. In addition, there is present from 0.01 to 5 parts by weight per 100 parts of the base polymer of a catalyst which with the acetoxy silane cross-linking agent is metal salt of a carboxylic acid. The most preferred catalyst are tin salts of carboxylic acids such as dibutyl tin dilaurate. Such composition with the base silanol polymer, the cross-linking agent and the tin salt are prepared and mixed in a substantially anhydrous state and the composition is packaged in a single package. Such a composition is therefore known as one-part RTV composition. When it is desired to cure the composition the seal on the package is broken and the composition is applied and simultaneously exposed to atmospheric moisture. Under those conditions, the composition will form a skin in as rapidly as 10 to 20 minutes and fully cure to a silicone elastomer in 24 hours.
There may be added other ingredients to the basic composition. One of these basic ingredients being from 4 to 400 parts of filler per 100 parts of the base polymer. The filler is desirably selected from reinforcing fillers such as fumed silica or precipitated silica which may be treated with such ingredients as cyclo polysiloxanes, along or in combination with silazenes. The advantage of treating the filler, specifically the reinforcing filler is to prevent a rapid viscosity build up in the composition in the uncure state while imparting the appropriately desired reinforcing properties to the composition. It is undesirable to add so much filler in the composition such that the composition has a viscosity build-up in the uncure state such that it is difficult to dispense from a tube, such as a caulking tube. Accordingly, it is highly desirable to treat the filler. Of course, there may be also added extending fillers to the composition, alone or in combination with the reinforcing fillers such as diatomaceous earth, lithopone, zinc oxide, iron oxide, groud quartz, and so forth. There may be added out the other ingredients to the composition such as a triorgano endstopped, diorganopolysiloxane, plastisizers, and other well known ingredients. Such addition of other ingredients to the basic composition form the basis of a great host of patents in the silicone field.
Irrespective of the above, it has been found that such silicone one-component RTV compositions are especially suitable as gasketing compositions or compositions for the formation of formed-in placed gaskets in automobiles. The reasons for the desirability of silicones as formed-in place gasketing material in automobiles is primarily due to their resistance to oil swell and also to their high temperature stability. Further, silicone have suitable weatherability characteristics. It should be noted that there are specific silicone compositions, one-component systems, that are improvements over the above basic composition that was discussed previously and can be formulated so that such compositions have further inhanced resistance to oil swell or even more inhance high temperature stability. The practice in the industry in the application of silicone and specifically one-component composition to form in place gaskets in automotive components has been dramatically diversed. On the one hand, there has been developed a great highly complicated computerized piece of machinery for automatically forming gaskets on automotive parts. Accordingly, such a computerized machinery normally operates by procedure by which the work piece is placed on the holding fixture and then anti-tie down buttons when pressed initiate the lowering of the nozzle to the work piece. Silicone material flows from the nozzle and transfer motion begins simultaneously automatically. The bead of silicone is dispensed in a uniform bead onto the work piece in a predetermined gasket pattern programed by either following a back line pattern via photo trace scrvodrive or multiple cams which drive the nozzle through the XY coordinates of the gasket pattern. At the precise moment that the gasket pattern is complete, the dispensing of the material is abruptly terminated and the nozzle is raised above the work piece. The work piece is then unloaded from the fixture and either assemblied to the mating part or set aside to cure. All the functions of such a piece of machinery are precisely timed and controlled by time-delay relays and interrelated magnetic relays which in turn controls pneumatic cylinders, electric motor drives, gear boxes to perform each vital function automatically and with precision. However, such machineries are highly complexed and normally require investment of $30,000 to $100,000 per machine depending on the functions or the variety of parts it is desired to be able to service with such a machine. Accordingly, not every business which fabricates assemblies which necessitates the presence of gaskets, is capable of investing in such a machine especially where the gasketing portion is a minor aspect of the total operation of the fabrication of the part. Accordingly, in small operations, it has been the custom to have an operator apply or form the placed gasket in a total manual manner from a tube. Accordingly, such a procedure involves the operator taking a tube of silicone and squeezing it on to a part and making a determination as to height of the tube from the part that is the thickness of the bead of silicone, the travel of the tube so as to form the path of silicone on the part and also the rate at which the silicone is dispensed on the part; all such functions in the application of the silicone bead being performed manually.
While such a method does not involve the large capital investment of the previous complex piece of machinery, nevertheless, it is a haphazard method and results in many poorly fabricated gaskets and a large rejection of poorly fabricated gasketed parts. Accordingly, it was highly desirable to have a relatively inexpensive piece of machinery which could be operated by an operator to put down or place a bead of gasketing silicone material on a automotive part wit precision and reliability from application to application and which could be utilized by an operator with facility and reliability.
Accordingly, it is one object of the present invention to provide for an inexpensive apparatus or machine which would apply uncured gasketing compositions to a part with facility and reliability.
It is another object of the present invention to provide for an inexpensive apparatus or machine which could be manually operated by an operator by which would automatically determine the thickness of the bead of the silicone material on the part and which would automatically determine the path of travel of the silicone on the part and which would automatically determine the amount of silicone that was applied as the bead on the part.
It is yet an additional object of the present invention to provide for an inexpensive apparatus for dispensing an uncured silicone gasketing composition to an assembly part which dispensing is carried out semi-automatically and efficiently, and in which the application of the silicone gasketing material is reproduceable from part to part.
It is still yet another object of the present invention to provide for an inexpensive apparatus for applying an uncured silicone gasketing composition to an automotive part which is done in a semi-automatic manner in which the application of the silicone bead is reproducable from part to part.
It is a further object of the present invention to provide for an inexpensive apparatus for applying a one component RTV silicone system as a gasketing composition to automotive parts in which the application of the one component RTV silicone system is semi-automatic.
These and other objects of the present invention are accomplished by means of the disclosure set forth here and below.